Aerodynamic Testing Research Articles

Application of CAD/CAE class systems to aerodynamic analysis of electric race cars

Aerodynamics is one of the most important factors which influence on every aspect of a design of a car and car driving parameters. The biggest influence aerodynamics has on design of a shape of a race car body, especially when the main objective of the race is the longest distance driven in period of time, which can not be achieved without low energy consumption and low drag of a car. Designing shape of the vehicle body that must generate the lowest possible drag force, without compromising the other parameters of the drive. In the article entitled „Application of CAD/CAE class systems to aerodynamic analysis of electric race cars” are being presented problems solved by computer analysis of cars aerodynamics and free form modelling. Analysis have been subjected to existing race car of a Silesian Greenpower Race Team. On a basis of results of analysis of existence of Kammback aerodynamic effect innovative car body were modeled. Afterwards aerodynamic analysis were performed to verify existence of aerodynamic effect for innovative shape and to recognize aerodynamics parameters of the shape. Analysis results in the values of coefficients and aerodynamic drag forces. The resulting drag forces Fx, drag coefficients Cx(Cd) and aerodynamic factors Cx*A allowed to compare all of the shapes to each other. Pressure distribution, air velocities and streams courses were useful in determining aerodynamic features of analyzed shape. For aerodynamic tests was used Ansys Fluent CFD software. In a paper the ways of surface modeling with usage of Realize Shape module and classic surface modeling were presented. For shapes modeling Siemens NX 9.0 software was used. Obtained results were used to estimation of existing shapes and to make appropriate conclusions.

Aerodynamic Effects of Anti-Icing Fluids on a Thin High-Performance Wing Section

The Federal Aviation Administration has worked with Transport Canada and others to develop allowance times for aircraft operating in ice-pellet precipitation based upon wind-tunnel experiments with a thin high-performance wing. These allowance times are applicable to many different airplanes. Therefore, the aim of this work is to characterize the aerodynamic behavior of the wing section in order to better understand the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination. Aerodynamic performance tests, boundary-layer surveys, and flow visualization were conducted at a Reynolds number of approximately and a Mach number of 0.12. Roughness and leading-edge flow disturbances were employed to simulate the aerodynamic impact of the anti-icing fluids and contamination. In the linear portion of the lift curve, the primary aerodynamic effect is the thickening of the downstream boundary layer due to the accumulation of fluid and contamination. This causes a reduction in lift coefficient and an increase in pitching moment (nose up) due to an effective decambering of the wing. The stalling characteristics of the wing with fluid and contamination appear to be driven at least partially by the effects of a secondary wave of fluid that forms near the leading edge as the wing is rotated in the simulated takeoff profile. These results have provided a much more complete understanding of the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination on this wing.

Aerodynamic Analysis of a Passenger Car at Yaw Angle and Two-Vehicle Platoon

Abstract Experimental and computational studies were performed to study the drag forces and the pressure distributions of a one-fifth scale model FIAT Linea at increasing yaw angle and two-vehicle platoon. Experiments were performed in the Uludag University Wind Tunnel (UURT) only for the yaw angles of 0 deg, 5 deg, and 10 deg due to the test section dimensional restriction. Supplementary tests were performed in the Ankara Wind Tunnel (ART) to evaluate the aerodynamic coefficients up to yaw angle of 40 deg. The test section blockage ratios were 20% and 1%, respectively, in the UURT and ART tunnels. The blockage effects for the yaw angles up to 10 deg were studied by the comparison of two wind tunnel results. The aerodynamic tests of two-vehicle platoon were performed in the ART tunnel at spacings of “x/L” 0, 0.5, and 1. Static pressure distributions were obtained from the model centerline and three vertical sections. In the numerical study, three-dimensional, incompressible, and steady governing equations were solved by star-ccm+ code with realizable k-ɛ two-layer turbulence model. Experimental and numerical Cp distributions and Cd values were found in good agreement for considered yaw angles and two-vehicle platoon. Maximum drag coefficient was obtained at yaw angle of 35 deg for both experimental and numerical calculations. The two-vehicle platoon analysis resulted with the significant drag coefficient improvement for the leading car at spacings of x/L = 0 and 0.5, while for the tail car drag coefficient remained slightly above the vehicle in isolation.

IDINTOS: the first prototype of an amphibious PrandtlPlane-shaped aircraft

This paper summarizes the main activities conducted to design, optimize and build a prototype of an innovative light amphibian. This aircraft is a “PrandtlPlane”, a particular box-wing configuration which introduces relevant advantages as increased aerodynamic efficiency and safety of flight; the research project, called IDINTOS, has been co-funded by the Regional Government of Tuscany (Italy), coordinated by the University of Pisa and carried out in 30 months by a consortium of public bodies and small private firms, starting from 2011. In this contribution an overview is given also on several aspects concerning the design, as the aerodynamic optimization, the construction and tests of three scaled models for towing tank wind tunnel and, flight tests, respectively.

When the Botulinium Toxin Injection Is Effective in Stutters

Background and Objectives Laryngeal hyperkinetic movements of stuttering patients is similar to that of adductor spasmodic dysphonia. There has been studies on implementing botulinium toxin injections to treat stuttering. However, the opinions on the bouolinium toxin injection's effects on stuttering patients vary. In this study authors aim to figure out when the botulinium toxin injection improves stuttering patients. Materials and Methods Stuttering patients who could receive botulinium toxin injection participated in this study. Age differences, gender differences, electroglottogrphic test, aerodynamic test in botulinium toxin injection treatment of stuttering were analyzed. Results The botulinium toxin injection had statistically significant impact on patients who showed low mean air flow rate during aerodynamic study. Conclusion The botulinium toxin injection could reduce stuttering of patients with low mean air flow rate in aerodynamic study. Key words: Botulinium toxin ㆍ Stutter ㆍ Mean air flow rate 핵심용어: ë³´íˆ´ë¦¬ëŠ„ë ì†Œì£¼ìž ìˆ ã† 말더듬 ㆍ í‰ê· í˜¸ê¸°ë¥˜ìœ¨

AERODYNAMIC RESISTANCE OF A BIOFILTER WITH A PACKING OF PINE CONES

The results of experiments on practical suitability of a biofilter packing made of natural materials – pinecones are provided. Geometric characteristics of a random packing of pine cones are calculated and compared with other types of packings of artificial and natural materials. Aerodynamic tests of the packing are carried out and obtained data are compared with the data for other packings. Some recommendations on improving the performance characteristics of the packing are suggested.

Experimental Installation for Studying Hydroaerothermal Characteristics of Sprinklers and Water Traps of Cooling Towers

An experimental installation designed for engineering tests of sprinkling and water trapping devices is described. Aerodynamic tests were performed to determine the aerodynamic resistance coefficient of sprinklers and water traps and its dependence on the recirculating water and air flow rate. Hydroaerothermal tests were performed to determine the relative circulating water temperature based on a host of physical parameters. The experimental installation developed permitted measurements of the key process parameters with fair accuracy.

Study Based on the AIAA Aerodynamic Design Optimization Discussion Group Test Cases

Three model problems associated with aerodynamic drag minimizations are studied. These test cases have been proposed by the aerodynamic design optimization discussion group, and they include an inviscid NACA0012 nonlifting airfoil, a viscous RAE2822 lifting airfoil, and a viscous lifting wing based on the NASA Common Research Model. Various optimization methods are used, including MDOPT, TRANAIR, SYN83, and SYN107. The resulting designed and associated baseline geometries are cross analyzed by several computational fluid dynamics codes, including OVERFLOW, TRANAIR, GGNS, and FLO82. Pathological issues are unveiled in both of the simple airfoil model problems. Designed geometries for the inviscid symmetric test case exhibit strong tendencies to permit nonsymmetric flow solutions. Designed airfoils for the viscous lifting case also support nonunique solutions and hysteresis loops at or near the design point in Reynolds-averaged Navier–Stokes and integral boundary-layer method simulations. These results provide further evidence that single-point aerodynamic optimization is often ill posed. In extreme cases, it can yield designs with very undesirable aerodynamic characteristics, at least as analyzed by Reynolds-averaged Navier–Stokes and integral boundary-layer methods occurring at offdesign, and even ondesign, conditions. These examples are used to further document the multiple-solution and pseudosolution phenomena for steady-state Reynolds-averaged Navier–Stokes. This provides evidence that, even in practical engineering settings, numerical methods to assess stability and uniqueness of steady-state solutions and/or predict the bifurcations of these solutions have value. The single-point wing design problem is likewise ill posed in the spanwise direction. A multipoint design with a potentially large number of points or the inclusion of inequality constraints can regularize the problem.

Aerodynamic Measures and Biofeedback as Management in Persistent Paradoxical Vocal Fold Motion and Reverse Phonation

Paradoxical vocal fold motion (PVFM) and reverse phonation are characterized by aberrant vocal fold adduction. To date, there have been no studies examining the aerodynamic events during reverse phonation. We present an unusual case of persistent reverse phonation secondary to respiratory distress associated with PVFM. Case report. We present the case of a 42-year-old female with sudden onset of respiratory distress associated with PVFM and persistent reverse phonation. She underwent baseline aerodynamic measurements followed by trial therapy. Through the use of instrumental and tactile aerodynamic biofeedback, the patient was able to coordinate exhalatory breath pressure flow during phonation, which resulted in immediately improved voice quality from highly dysphonic to nearly normal voice quality. Patients with reverse phonation seldom undergo aerodynamic testing as part of the initial diagnostic and management program. Our case study demonstrates the effectiveness of aerodynamic technology to enable a patient with aberrant glottic function to recognize inspiratory phonation events and to reestablish consistent expiratory flow/pressure egress in speech tasks. Instrumental and tactile biofeedback is effective for reinforcement of normal flow patterns during speech tasks.

Study of the average heat transfer coefficient at different distances between wind tunnel models

The paper presents investigations of physical and climatic factors with regard to design and process variables having effect on heat transfer in the building model system at different distances between them in the airflow direction. The aim of this work is to improve energy efficiency of exterior walls of buildings. A method of physical simulation was used in experiments. Experimental results on the average values of the heat transfer coefficient in the building model system are presented herein. A series of experiments was carried out on a specific aerodynamic test bench including a subsonic wind tunnel, heat models and devices for giving thermal boundary conditions, transducers, and the record system equipment. The paper contains diagrams of the average heat transfer distribution at fixed Reynolds number and the airflow angle of attack; the average values of the heat transfer coefficient for each face and wind tunnel models as a whole at maximum, medium, and large distances between them. Intensification of the average heat transfer was observed on the downstream model faces depending on the distance between models.

Noise Reduction in Gas Ducts by Multistage Mufflers with Improved Technical and Economic Characteristics

Results from acoustic and aerodynamic tests of a multistage noise muffler with different plate thicknesses built according to original recommendations are reported. The locations of the stages of the muffler are determined by mathematical modelling based on their having minimal aerodynamic drag and the lengths of the stages with different plate thicknesses are determined by minimizing the cost. The tests show that the muffler has high acoustic efficiency and low aerodynamic drag. The approaches considered here have been used in developing two-stage plate mufflers for a thermal power plant in Moscow.

Extension of the Range of the Stable Operation of the Stage of the Centrifugal Compressor by Actuating Medium Blowing in the Vaneless Diffuser

This paper gives the results of the experimental investigation of the blowing in the vaneless diffuser used for the centrifugal compressor stage. The investigation was carried out using the aerodynamic test bench of the PJSC “Frunze Scientific and Industrial Agglomeration”. The blowing was performed in the radial direction; the inflated air was supplied by the external source. The experimental investigation allowed us to determine the influence of the flow rate of the inflated air on the boundary of the surge occurrence and on the dimensionless characteristics of the stage. It has been proved that the blowing in the vaneless diffuser allows us to extent the range of the stable operation of the stage in the domain of low efficiencies.

Power Supply for a Wireless Sensor Network: Airliner Flight Test Case Study

— In this paper we present hands-on experience related to on-going implementation in aircraft of power supply for a wireless sensor network deployed for aerodynamic flight tests. This autonomous battery-free power supply is capturing, managing and storing primary energy from the environment, using solar light and photovoltaic cells. For practical purposes, it is also equipped with an auxiliary power input. The specifications are detailed, the general architecture is presented and justified, and test results are discussed.

A high‐order discontinuous Galerkin method for all‐speed flows

SUMMARYIn this article, we present a discontinuous Galerkin (DG) method designed to improve the accuracy and efficiency of steady solutions of the compressible fully coupled Reynolds‐averaged Navier–Stokes and k − ω turbulence model equations for solving all‐speed flows. The system of equations is iterated to steady state by means of an implicit scheme. The DG solution is extended to the incompressible limit by implementing a low Mach number preconditioning technique. A full preconditioning approach is adopted, which modifies both the unsteady terms of the governing equations and the dissipative term of the numerical flux function by means of a new preconditioner, on the basis of a modified version of Turkel's preconditioning matrix. At sonic speed the preconditioner reduces to the identity matrix thus recovering the non‐preconditioned DG discretization. An artificial viscosity term is added to the DG discretized equations to stabilize the solution in the presence of shocks when piecewise approximations of order of accuracy higher than 1 are used. Moreover, several rescaling techniques are implemented in order to overcome ill‐conditioning problems that, in addition to the low Mach number stiffness, can limit the performance of the flow solver. These approaches, through a proper manipulation of the governing equations, reduce unbalances between residuals as a result of the dependence on the size of elements in the computational mesh and because of the inherent differences between turbulent and mean‐flow variables, influencing both the evolution of the Courant Friedrichs Lewy (CFL) number and the inexact solution of the linear systems. The performance of the method is demonstrated by solving three turbulent aerodynamic test cases: the flat plate, the L1T2 high‐lift configuration and the RAE2822 airfoil (Case 9). The computations are performed at different Mach numbers using various degrees of polynomial approximations to analyze the influence of the proposed numerical strategies on the accuracy, efficiency and robustness of a high‐order DG solver at different flow regimes. Copyright © 2014 John Wiley & Sons, Ltd.

Tuning a digital multivariable controller for a lab-scale helicopter system via simulated annealing and evolutionary algorithms

Helicopter systems are considered a complex and challenging control problem due to strong couplings and high non-linearities. In this paper, simulated annealing (SA), as one of the leading methods in search and optimization, is applied to tune a multivariable controller of a lab-scale helicopter system. The lab-scale helicopter system is a multivariable experimental aerodynamic test rig that resembles the behaviour of a real helicopter. The control objectives are quickly to reach a desired position or track a trajectory. A centralized cross-coupled PID controller is used to achieve these objectives. First, SA optimizations are carried out with 24 different initial configurations. Then, the best results of these SA configurations are compared with other controllers obtained with evolutionary algorithms (EAs) of genetic algorithms (GAs), modified particle swarm optimization (MPSO) and differential evolution (DE). The comparisons are based on statistical measures of 20 independent trials, non-linear computer simulations of different input signals and real-time measurements for various commands of positions or trajectories. Results show that SA obtained the best performance index and acceptable time-domain performance on reaching hovering point, following a step command and tracking a sine trajectory compared with the investigated EAs.

Shifts in stability and control effectiveness during evolution of Paraves support aerial maneuvering hypotheses for flight origins.

The capacity for aerial maneuvering was likely a major influence on the evolution of flying animals. Here we evaluate consequences of paravian morphology for aerial performance by quantifying static stability and control effectiveness of physical models for numerous taxa sampled from within the lineage leading to birds (Paraves). Results of aerodynamic testing are mapped phylogenetically to examine how maneuvering characteristics correspond to tail shortening, forewing elaboration, and other morphological features. In the evolution of Paraves we observe shifts from static stability to inherently unstable aerial planforms; control effectiveness also migrated from tails to the forewings. These shifts suggest that a some degree of aerodynamic control and capacity for maneuvering preceded the evolution of a strong power stroke. The timing of shifts also suggests features normally considered in light of development of a power stroke may play important roles in control.

Periodic transonic flow simulation using fourier-based algorithm

The present research simulates time-periodic unsteady transonic flow around pitching airfoils via the solution of unsteady Euler and Navier-Stokes equations, using time spectral method (TSM) and compares it with the traditional methods like BDF and explicit structured adaptive grid method. The TSM uses a Fourier representation in time and hence solves for the periodic state directly without resolving transients (which consume most of the resources in a time-accurate scheme). Mathematical tools used here are discrete Fourier transformations. The TSM has been validated with 2D external aerodynamics test cases. These test cases are NACA 64A010 (CT6) and NACA 0012 (CT1 and CT5) pitching airfoils. Because of turbulent nature of flow, Baldwin-Lomax turbulence model has been used in viscous flow analysis with large oscillation amplitude (CT5 type). The results presented by the TSM are compared with experimental data and the two other methods. By enforcing periodicity and using Fourier representation in time that has a spectral accuracy, tremendous reduction of computational cost has been obtained compared to the conventional time-accurate methods. Results verify the small number of time intervals per pitching cycle (just four time intervals) required to capture the flow physics with small oscillation amplitude (CT6) and large oscillation amplitude (CT5) as compared to the other two methods.

The characterisation of a gust generator for aerodynamic testing

An experimental investigation was conducted to characterise the gust environment generated by a cascade of sinusoidally oscillating vanes in the Cranfield University 1.52 m by 1.14 m low-speed, open-jet, closed-circuit wind tunnel operating at 7.5 ms−1 and 14.5 ms−1. Measurements were made at four stream-wise and three vertical positions in the flow-field downstream of the vanes using a cross-wire anemometer. The oscillation angle of the vanes was set at ±8° and ±12° with frequencies of 0.5 Hz, 1.0 Hz and 2.0 Hz corresponding to a reduced frequency of between 0.01 and 0.07. The vertical components of velocity and turbulence intensity were shown to be consistent for the range of measurement points chosen. The peak vertical velocity component downstream of the vanes was shown to be proportional to the maximum vane angle of attack but largely independent of reduced frequency.

Performance of a Micro-UAV lifting system built with the usage of rapid prototyping methods

This article presents results of the aerodynamic testing of a micro unmanned aerial vehicle rotor efficiency. The rotors were prepared as a set of two rotors in a counter-rotating ducted drive. Prototypes of the drives were made using two rapid prototyping techniques – FDM – fused deposition modelling method and SLS – selective laser sintering. Rotors were made then treated by introducing additional finishing cyanoacrylate coating and abrasive processing. Main differences between those models were observed in fan shape, porosity, surface roughness and mechanical properties – stiffness. An influence of these factors was observed on an aerodynamic efficiency. For the obtained prototypes both simulations and experimental testing were conducted with thrust, power, torque measurements, as well as the measurement of velocity and pressure distribution at the outlet of the duct. The results show the possibility of using rapid prototyping techniques to produce prototypes of drives operating in the low and medium Reynolds numbers (6000-60000), and the aerodynamic shape relevant factors affecting the preparation and performance of such drives. In addition, simulation studies were performed using the Fluent environment where experimental results were confronted with the results of simulation studies.

Application of 3D printing technology in aerodynamic study

3D printing, as an additive process, offers much more than traditional machining techniques in terms of achievable complexity of a model shape. That fact was a motivation to adapt discussed technology as a method for creating objects purposed for aerodynamic testing. The following paper provides an overview of various 3D printing techniques. Four models of a standard NACA0018 aerofoil were manufactured in different materials and methods: MultiJet Modelling (MJM), Selective Laser Sintering (SLS) and Fused Deposition Modeling (FDM). Various parameters of the models have been included in the analysis: surface roughness, strength, details quality, surface imperfections and irregularities as well as thermal properties.